Mikael--I'm sort of the club's acknowledged Campy Wheel Dork, as I've made it a special hobby of mine to document all the variations. There were no less than six different wheels produced from 1970-1974 in the 7- and 8-inch variety: three-slot, one-slot, early Pre-L two-slot, late Pre-L two-slot, early L two-slot and late L two-slot.
The ten-inch wheels are a different story altogether. I've counted three very different variations, but can't swear that there aren't sub-variations beyond that. In your photos, the bottom wheel, with the full-length ribs, is the very early style first introduced in late 1972 I think.
You can check the date of your wheel as it's stamped on the back side. There is a circle with the two digits of the production year; this is surrounded by a sundial-looking arrangement with raised dots, and those dots correspond to the month. So, a sundial with six dots and the number "72" in the middle means the wheel was made in June '72. (The same holds true for all the other Campy wheels, including GT5 wheels).
Your top photo shows a later variation of the 10-inch wheel, and I'd guess it was cast in the late 70s or early 80s. The hub in the center isn't particularly beefy. The later wheels (like the ones I have from 1989) are much more substantial in the center.
Here's a link to photos of my two sets of 10-inch wheels on the POCA website, with 1982-era wheel on the left and 1989-era wheel on the right. There are about ten differences (give or take) between them--can you spot them all? 10-inch Campy wheel differences
(yes I know my avatar photo doesn't come up properly anymore....)